Spore development in species of Periconia II. P. byssoides and P. igniaria

Abstract

Conidia of Periconia byssoides are produced either micronematously on branched or unbranched chains from undifferentiated conidiophores, or macronematously on thickened, brown, septate conidiophores. Micronematous production is similar to that reported in P. prolifica , i.e. the basipetal septation of an elongated conidiogenous cell. The conidiogenous cell at the apex of macronematous conidiophores gives rise polyblastically to numerous chains of conidia, each of which develops by a holobastic process from the apex of a conidium or conidiogenous cell. The youngest conidium at the apex of each chain is, however, the first to develop the characteristic verrucose ornamentation, maturation being basipetal within the chain. In Periconia igniaria no large heads of conidia are produced; the conidiogenous cell at the apex of the conidiophore gives rise to a few conidial chains by a holoblastic process, though further back from the apex spores may be produced by the septation of an elongated conidiogenous cell. Conidia at the apex of a chain develop their mature, spiny ornamentation first; ornamentation in both fungi is brought about by a separation of the thin, outer pellicle from the rest of the wall followed by melanin deposition within these excrescences.